Method for extracting bitumen from an aged oil sands ore stream

ABSTRACT

The present invention provides a method for extracting bitumen from an aged oil sands ore stream, the method comprising at least the steps of:
         (a) providing an aged oil sands ore stream, the oil sands ore stream containing connate water;   (b) contacting the aged oil sands ore stream with a solvent thereby obtaining a solvent-diluted oil sand slurry;   (c) filtering the solvent-diluted oil sand slurry obtained in step (b), thereby obtaining a solids-depleted stream and a solids-enriched stream;   (d) removing solvent from the solids-depleted stream obtained in step (c) thereby obtaining a bitumen-enriched stream;
 
wherein the solvent as used in step (b) comprises a non-aqueous solvent; and
 
wherein the connate water in the aged oil sands ore stream as provided in step (a) has a sulphate concentration of at least 50 ppmv, as determined by ASTM D516.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/918,315 filed Dec. 19, 2013, which is incorporated herein by reference.

BACKGROUND

The present invention relates to a method for extracting bitumen from an aged oil sands ore stream.

Various methods have been proposed in the past for the recovery of bitumen (sometimes referred to as “tar” or “bituminous material”) from oil sands as found in various locations throughout the world and in particular in Canada such as in the Athabasca district in Alberta and in the United States such as in the Utah oil sands.

Typically, oil sand (also known as “bituminous sand” or “tar sand”) comprises a mixture of bitumen (in this context also known as “crude bitumen”, a semi-solid form of crude oil; also known as “extremely heavy crude oil”), sand, clay minerals and water. Usually, oil sand contains about 5 to 25 wt. % bitumen (as meant according to the present invention), about 1 to 13 wt. % water, the remainder being sand and clay particles.

As an example, it has been proposed and practiced at commercial scale to recover the bitumen content from the oil sand by mixing the oil sand with water (‘aqueous extraction’) and separating the sand from the aqueous phase of the slurry formed.

A problem of such aqueous extraction of bitumen from oil sand is that—apart from that large amounts of water are to be used—bitumen cannot be properly extracted from aged ore (sometimes also called ‘oxidized ore’ or ‘weathered ore’). This phenomenon of poor processability of aged ore has for instance been described in the article by Liu et al. “Processability of Oil Sand Ores in Alberta”, Energy & Fuels, 2005, 19, 2056-2063.

It is an object of the present invention to improve the bitumen extraction from aged oil sand ore.

One or more of the above or other objects may be achieved according to the present invention by providing a method for extracting bitumen from an aged oil sands ore stream, the method comprising at least the steps of:

-   -   (a) providing an aged oil sands ore stream, the oil sands ore         stream containing connate water;     -   (b) contacting the aged oil sands ore stream with a solvent         thereby obtaining a solvent-diluted oil sand slurry;     -   (c) filtering the solvent-diluted oil sand slurry obtained in         step (b), thereby obtaining a solids-depleted stream and a         solids-enriched stream;     -   (d) removing solvent from the solids-depleted stream obtained in         step (c) thereby obtaining a bitumen-enriched stream;         -   wherein the solvent as used in step (b) comprises a             non-aqueous solvent; and         -   wherein the connate water in the aged oil sands ore stream             as provided in step (a) has a sulphate concentration of at             least 50 ppmv, as determined by ASTM D516.

It has now surprisingly been found according to the present invention that non-aqueous extraction allows to process aged ore in an aged oil sands ore stream.

A further advantage of the present invention is that by using a non-aqueous extraction process the need for large quantities of process water is reduced. Unlike the aqueous extraction process, the method according to the present invention does generate large volumes of wet tailings that require large tailings ponds for storage and long recovery times.

According to the present invention, the providing of the aged oil sands ore stream in step (a) can be done in various ways. Typically, the oil sands ore is reduced in size, e.g. by crushing, breaking and/or grinding, to below a desired size upper limit Preferably, the oil sands ore provided in step (a) has a particle size of less than 20 inch, preferably less than 16 inch, more preferably less than 12 inch. Also, the oil sands ore stream provided in step (a) is typically subjected to a deoxygenation step.

As mentioned above, the connate water in aged the oil sands ore stream as provided in step (a) has a sulphate concentration of at least 50 ppmv, as determined by ASTM D516. This lower limit for the sulphate content in the connate water is believed to be a proper reflection of an aged ore (see Table 2 hereafter). Preferably, the connate water in the aged oil sands ore stream as provided in step (a) has a sulphate concentration of at least 80 ppmv, preferably at least 100 ppmv, as determined by ASTM D516.

Also it is preferred that the connate water in the aged oil sands ore stream as provided in step (a) has a magnesium concentration of at least 3.0 ppmv, preferably at least 4.0 ppmv, more preferably at least 5.0 ppmv, as determined by ASTM D511.

Further it is preferred that the connate water in the aged oil sands ore stream as provided in step (a) has a calcium concentration of at least 4.0 ppmv, preferably at least 5.0 ppmv, more preferably at least 10.0 ppmv, as determined by ASTM D511. Furthermore it is preferred that the connate water in the aged oil sands ore stream as provided in step (a) has a pH of at most 7.5, as determined by ASTM D1293. Also it is preferred that the aged oil sands ore stream as provided in step (a) has a moisture content of at most 3.0 wt. %, based on the oil sands ore stream, preferably at most 2.5 wt. %, more preferably at most 2.0 wt. % even more preferably at most 1.8 wt. %.

In step (b), the aged oil sands ore stream is contacted with a solvent thereby obtaining a solvent-diluted oil sand slurry. As mentioned above, according to the present invention, the solvent as used in step (b) comprises a non-aqueous solvent. The person skilled in the art will understand that, in particular when the solvent is recycled from a downstream point in the process, it may contain bitumen.

The solvent as used in the method of the present invention may be—provided that it comprises a non-aqueous solvent—selected from or composed of a wide variety of solvents, including water, aromatic hydrocarbon solvents and saturated or unsaturated aliphatic (i.e. non-aromatic) hydrocarbon solvents; aliphatic hydrocarbon solvents may include linear, branched or cyclic alkanes and alkenes and mixtures thereof. Preferably, the solvent in step (b) comprises an aliphatic hydrocarbon having from 3 to 9 carbon atoms per molecule, more preferably from 4 to 7 carbons per molecule, or a combination thereof. Especially suitable solvents are saturated aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, octane and nonane (including isomers thereof), in particular butane, pentane, hexane and heptane. It is preferred that the solvent in step (b) comprises at least 90 wt. %, preferably at least 95 wt. %, of the non-aqueous solvent (and in particular of the aliphatic hydrocarbon having from 3 to 9 carbon atoms per molecule). Also, it is preferred that in the solvent of step (b) substantially no aromatic solvent (such as toluene or benzene) is present, i.e. less than 5 wt. %, preferably less than 1 wt. %. Further it is preferred that a single solvent is used as this avoids the need for a distillation unit or the like to separate solvents. Also, it is preferred that the solvent has a boiling point lower than that of the bitumen to facilitate easy separation and recovery.

Furthermore, if desired, additional process fluids may be added, such as water and/or agglomeration agents, for example to aid in achieving desired slurry properties through agglomeration of fine particles.

In step (c), the solvent-diluted oil sand slurry obtained in step (b) is filtered, thereby obtaining a solids-depleted stream and a solids-enriched stream. This filtration step is not limited in any way. As the person skilled in the art is familiar with how to perform such a filtration step, this is not further discussed here in detail. If desired, before the filtration of step (c), a screening step may be performed to remove undesired oversized material. Typically, the solvent-diluted oil sand slurry obtained in step (b) is allowed to settle before being filtered in step (c).

In step (d), solvent is removed from the solids-depleted stream obtained in step (c) thereby obtaining a bitumen-enriched stream. This bitumen-enriched stream may be sent to a refinery or the like for further processing. As the person skilled in the art is familiar with how to remove the solvent and process the bitumen-enriched stream, this is not further discussed here in detail.

Hereinafter the invention will be further illustrated by the following non-limiting Examples.

EXAMPLES

An oil sand ore containing about 10 wt. % bitumen and with the characteristic as given in Table 1 below was put in an open container to allow exposure of the ore to room temperature. Samples were taken from the top of the container after 4 weeks and 6 months and subjected to the process of contacting with solvent, settling and filtration as described below. Also, samples were taken at the start (‘fresh’) and at these three times for connate water tests; the concentration of various components in the connate water of the samples and some properties thereof are given in Table 2. As can be seen from Table 2, several properties (in particular sulphate, magnesium and calcium concentration and pH) change over time when the ore is ageing.

TABLE 1 Component Amount [wt. %] bitumen 11.9 connate water 3.2 Fines 9.4  <2 μm 1.0 <44 μm 9.4 <74 μm 11.0

TABLE 2 fresh 4 weeks 6 months Sulphate¹ [ppmv] 7.0 140.0 109.7 Magnesium² [ppmv] 1.0 13.2 9.7 Calcium² [ppmv] 1.4 27.8 24.3 Silica [ppmv] 3.7 0.2 0.3 Aluminum [ppmv] 1.5 <0.1 <0.1 Iron [ppmv] 0.4 <0.01 <0.01 pH 7.8 6.9 6.8 Moisture content³ [wt %] 1.5 0.7 0.1 ¹determined by ASTM D516 ²determined by ASTM D511 ³determined by Karl Fischer titration measured after extraction and filtration. [An oil sand sample (20 to 40 gram) was poured into 250 ml solvent mixture (containing 74% toluene and 26% isopropyl alcohol). The obtained slurry was mixed in a tumbler for 24 h at 15 rpm and subsequently allowed to settle for 30 min. Part of the supernatant liquid was filtered over a 0.45 μm PVDF membrane Luer-lock syringe filter. About 0.2 ml was taken from the filtered liquid and analyzed by volumetric Karl Fischer titration for water content whilst using Hydranal Composite 5 as titrant.]

Reference Example 1 (Not According to the Present Invention, as Not an Aged Ore)

750 g fresh oil sands ore was subjected to the following process of contacting with solvent, settling and filtration. The ore was contacted for 30 min on a low shear mixing tumbler with a calculated amount of n-pentane to provide an S/B (solvent to bitumen) weight ratio of 2.3 thereby obtaining solvent-diluted oil sand slurry. The slurry was poured into a settle tube and allowed to settle for 10 minutes and taken for filtration. In the filtration unit, a first amount of 139 g n-pentane was used as a wash liquid; at a pressure difference of 0.3 bar it took 6 seconds for the wash liquid to penetrate into the filter cake. A second amount (again 139 g) of n-pentane was used and at the pressure difference of 0.3 bar it took 3 seconds for the wash liquid to penetrate into the filter cake. Filtration times and bitumen recovery are given in Table 3.

Examples 1-2

The procedure of Reference Example 1 was repeated for the ore samples taken at 4 weeks (Example 1) and 6 months (Example 2).

Comparative Example 1

Aged ore was extracted with water as the extraction solvent; however, this resulted in undesirably low bitumen recovery.

TABLE 3 Reference Ex. 1 Ex. 1 Ex. 2 Filtration time (first 6 7 24 amount of wash liquid) [s] Filtration time 3 4 11 (second amount of wash liquid) [s] Bitumen recovery [%] 83 81 82

Discussion

As can be seen from Table 3, non-aqueous bitumen extraction of aged ores (having a sulphate concentration of at least 50 ppmv) resulted in surprisingly desirable bitumen recovery.

The person skilled in the art will readily understand that many modifications may be made without departing from the scope of the invention. Further, the person skilled in the art will readily understand that, while the present invention in some instances may have been illustrated making reference to a specific combination of features and measures, many of those features and measures are functionally independent from other features and measures given in the respective embodiment(s) such that they can be equally or similarly applied independently in other embodiments. 

We claim:
 1. A method for extracting bitumen from an aged oil sands ore stream, the method comprising at least the steps of: (a) providing an aged oil sands ore stream, the oil sands ore stream containing connate water; (b) contacting the aged oil sands ore stream with a solvent thereby obtaining a solvent-diluted oil sand slurry; (c) filtering the solvent-diluted oil sand slurry obtained in step (b), thereby obtaining a solids-depleted stream and a solids-enriched stream; (d) removing solvent from the solids-depleted stream obtained in step (c) thereby obtaining a bitumen-enriched stream; wherein the solvent as used in step (b) comprises a non-aqueous solvent; and wherein the connate water in the aged oil sands ore stream as provided in step (a) has a sulphate concentration of at least 50 ppmv, as determined by ASTM D516.
 2. The method according to claim 1, wherein the connate water in the aged oil sands ore stream as provided in step (a) has a sulphate concentration of at least 80 ppmv, preferably at least 100 ppmv, as determined by ASTM D516.
 3. The method according to claim 1, wherein the connate water in the aged oil sands ore stream as provided in step (a) has a magnesium concentration of at least 3.0 ppmv, preferably at least 4.0 ppmv, more preferably at least 5.0 ppmv, as determined by ASTM D511.
 4. The method according to claim 1, wherein the connate water in the aged oil sands ore stream as provided in step (a) has a calcium concentration of at least 4.0 ppmv, preferably at least 5.0 ppmv, more preferably at least 10.0 ppmv, as determined by ASTM D511.
 5. The method according to claim 1, wherein the connate water in the aged oil sands ore stream as provided in step (a) has a pH of at most 7.5, as determined by ASTM D1293.
 6. The method according to claim 1, wherein the aged oil sands ore stream as provided in step (a) has a moisture content of at most 3.0 wt. %, based on the oil sands ore stream, preferably at most 2.5 wt. %, more preferably at most 2.0 wt. % even more preferably at most 1.8 wt. %. 